Water-based fluids such as, for example, drilling fluids, milling fluids, mining fluids, water-based metal working fluids, food additives and water-based paints, are useful in a variety of industrial applications. It is well known to those skilled in the art of drilling wells to tap subterranean deposits of natural resources, such as gas, geothermal steam or oil, especially when drilling by the rotary method or the percussion method wherein cuttings must be removed from the bore hole, it is necessary to use a drilling fluid.
The use of water-based fluids in, for example, workover and completion fluids in oil field operations is also well known to those skilled in the art. Workover fluids are those fluids used during remedial work in a drilled well. Such remedial work includes removing tubing, replacing a pump, cleaning out sand or other deposits, logging, etc. Workover also broadly includes steps used in preparing an existing well for secondary or tertiary recovery such as polymer addition, micellar flooding, steam injection, etc.
Completion fluids are those fluids used during drilling and during the steps of completion, or recompletion, of the well. Completion operation can include perforating the casing, setting the tubing and pump, etc. Both workover and completion fluids are used in part to control well pressure, to stop the well from blowing out while it is being completed or worked over, or to prevent the collapse of casing from over pressure.
Additives, chemicals or other materials, are often added to the water-based fluids for various reasons that include, but are not limited to, controlling water loss, increasing viscosity, reducing corrosion, inhibiting biodegradation, and increasing the density of the fluids. For example, chemicals such as, for example, water-thickening polymers serve to increase the viscosity of the water-based fluids, when used as workover fluids or completion fluids, to retard the migration of the brines into the formation and to lift drilled solids from the wellbore.
However, unless proper precautions are taken, these water-thickening polymers, when mixed into a water-based fluid, agglomerate to form partially hydrated polymer lump commonly called "fish-eyes" which are extremely slow to dissolve. Furthermore, the "fish-eyes" are often screened out with drilled solids by solids control equipment commonly used in the oil field operations. This leads to problems such as, for example, plugging of a shale shaker screen, poor performance of the polymers, and combinations thereof.
Dry additives other than polymers, for example, carbon black, neutralized asphalt sulfonate, lignite and combinations thereof, are insoluble or partially soluble in water or water-based fluids. The dry additives, besides causing the plugging problems, can be harmful to the health of workers if proper precautions are not taken when using the additives.
Liquid additives and processes therefor have been developed to overcome some of the problems associated with using dry additives. For example, although U.S. Pat. No. 5,091,448 provides an excellent stable liquid additive and process for preparing the stable liquid additive suspension, the liquid additive contains a hydrocarbon as a liquid carrier. Unfortunately, because hydrocarbons are in the liquid additive, it cannot be used in some areas where environmental regulations are of concern. U.S. Pat. No. 5,114,597 discloses a process for manufacturing a water-based drilling fluid wherein the process comprises mixing a hydrophobic carbon black and either a surfactant or a dispersant followed by shearing the resulting mixture to convert the hydrophobic carbon black to hydrophilic carbon black. However, a usable liquid additive of neutralized asphalt sulfonate or a blend that contains neutralized asphalt sulfonate as a component cannot be prepared by the process disclosed in the '597 patent because the additive becomes too viscous or solids settle out at the bottom of the additive.
It is therefore highly desirable to develop a liquid suspension composition which remains stable and is usable as an additive in water or water-based fluid. It would also be a significant contribution to the art if a stable liquid suspension composition that is also environmentally friendly for use in oil field applications is developed.